112
FXUS63 KILX 281728
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1128 AM CST Fri Feb 28 2025

.KEY MESSAGES...

- Strong wind gusts and warm, dry conditions will result in
  elevated fire danger across much of the region this afternoon.
  Any fires that start may quickly grow out of control. Burning is
  discouraged today.

- A Wind Advisory includes portions of central and east-central
  Illinois. Westerly gusts of 40-50 mph are expected in the
  advisory area during the late morning and early afternoon, with
  peak gusts of 30-45 mph elsewhere.

- Temperatures turn much colder this weekend, dropping from the
  mid/upper 60s today to mid 30s to low 40s on Saturday-Sunday.

- Multiple disturbances will bring precip chances early next week,
  with the highest precip chances being Tuesday afternoon/evening
  (80- 90% chance). There is some potential for strong to severe
  storms on Tuesday.

&&

.UPDATE...
Issued at 905 AM CST Fri Feb 28 2025

A period of windy and unseasonably warm weather conditions is on tap
for this Friday. Forecast highs this afternoon were bumped up a
couple degrees (south of roughly I-72) in line with the latest
iterations of the RAP and HRRR, which suggest highs could reach the
upper 60s near and south of roughly the I-72 corridor. Driven by a
fading LLJ, strong southwest winds (gustiest across east-central IL)
this morning will weaken briefly early afternoon, but even as winds
aloft weaken another period of gusts over 35 mph will occur behind a
pre-frontal trough beginning mid afternoon with deeper mixing. The
actual cold front arrives during the evening from north to south and
behind it a surge of subsidence would help transport momentum to the
surface for continued strong gusts, however by this time mixing is
less diurnally favored so confidence is lower in whether the gusty
winds will continue. The best chance appears to be near and north of
roughly I-72 where the CAMs suggest the front will arrive around 7-
8pm. Knowing how cold advection can keep us mixed and cause surface
winds to verify near the high end of guidance, we suspect the Wind
Advisory, in effect for the eastern CWA this morning, may need to be
extended in space and time, or another one may be issued to cover
the second round of strong gusts this afternoon and evening;
however, we`ll hold off for now and keep a cautious eye on upstream
obs before pulling the trigger on anything just yet.

Another thing we`ll be monitoring today is the potential for hitting
Red Flag Criteria during the afternoon. Based on how dry conditions
are aloft on the 12z ILX raob and the anticipated gusty winds, we
suspect it`ll be close for each condition. Ultimately, we`re going
to keep an eye on surface obs but for now maintain the SPS, aiming
to make a decision on whether to extend that headline or replace it
with a RFW by midday. Thinking hasn`t changed much from early this
morning, so the fire weather discussion remains relevant.

Bumgardner

&&

.DISCUSSION...
Issued at 308 AM CST Fri Feb 28 2025

*** THROUGH THIS WEEKEND ***

A deepening sfc low will track from just north of MN early this
morning to the UP of Michigan by this afternoon. In response to
the tightly packed pressure gradient, an expansive wind field will
result in strong wind gusts and elevated fire danger across the
region. Portions of west-central IL are included in the "Elevated"
category of the Day 1 SPC Fire Weather Outlook, and portions of
central and east-central IL are under a Wind Advisory. Additional
details on the fire weather threat are included in the Fire
Weather section of the AFD.

The peak gusts today will be driven in large part by the placement
of a decaying LLJ and the onset of deeper diurnal mixing. The LLJ
(925mb/1500` AGL winds in excess of 50 knots) is progged to shift
from west to east across the area after 12z/6am, with the bulk of
the 40+ kt 925mb winds located east of I-55 by midday, with
lighter 925mb winds to the west. The expectation is that as the
LLJ moves over most areas west of I-55/south of I-74 during the
morning, the mixing will be insufficient to bring advisory level
gusts (45+ mph) to the sfc, but as the jet moves east into the
late morning/early afternoon and mixing deepens those 45+ mph
gusts translate to the ground. Probabilistic guidance from the 00z
HREF and 01z NBM are in line with this, with the highest
probabilities (50-70%) of exceeding wind advisory criteria (45+
mph gusts) being across east-central IL. That being said, there is
some potential for mixing to overperform which could lead to a
brief period of 45+ mph gusts during the mid/late morning (9a-12p)
across Knox, Fulton, Peoria, and Tazewell counties (20-40%
chance). Confidence was not high enough to expand the advisory
into these counties, and if such gusts do occur it should be a
relatively short window. Winds will be out of the southwest during
the morning, turning to west-northwesterly by mid- afternoon.

Temps will be well above normal today, in the mid/upper 60s. Cold
FROPA associated with the aforementioned sfc low will occur this
evening, with sharply colder air in place for Sat. HREF mean 850mb
temps plummet from around +9 degC today to around -13 degC by
Sat. High temps are forecast to be as much as 20-25 degF cooler
tomorrow, falling into the mid/upper 30s, which is about 5-10 degF
below normal. Northwesterly winds sustained at 10-15 mph will
make it feel even cooler. As a sfc high shifts over the region
Sun, winds become lighter, but temps remain on the cool side, in
the upper 30s or low 40s. Dry weather is expected through the
weekend.

*** NEXT WEEK ***

Next week will feature two disturbances during the first half of
the work week, with the first expected to be a weaker shortwave
through on Mon, with a 30-40% chance of precip. P-type remains
somewhat uncertain. Current forecast soundings show sfc-800mb
temps above freezing, but the sfc wet-bulb is near freezing during
the morning hours as precip moves in (before warming above
freezing into the afternoon). This suggests some potential for
rain or snow at the onset, before changing to all rain into the
day. If sfc temps trend sharply cooler with this system, icing
could come into play, but probabilistic guidance finds this a very
unlikely outcome, with less than a 5% chance for any freezing
rain on Mon.

A deeper trough emerges Tues AM and is likely to result in an
anomalous sfc low tracking across the Midwest. Both the NAEFS and
GEFS depict MSLP values below the minimum of their respective
climatologies for this time of year, with forecast MSLP values
below 990mb. Precip chances are highest Tues afternoon-evening
(80-95% chance) but remain over 60% through Tues night-Wed AM.
Unlike previous low pressure systems, this system should have open
access to Gulf moisture, and some deterministic models have a sfc
Td plume approaching 60 degF advecting into the ILX CWA. Ens mean
PWAT values approach 1.25", which is near the max of the ILX
sounding climatology for early March.

This combination of potent dynamics and unseasonable moisture
introduce potential for severe storms and flooding. Early
indications suggest a low CAPE/moderate-to-high shear environment,
with a 20-40% chance of 250+ J/kg of CAPE and 40+ knots of deep
layer shear. Both the CIPS analogs and CSU machine learning
guidance have a 15% severe storm risk across southwestern
portions of the ILX CWA on Tues. The greatest potential for severe
weather is likely to be focused south of the ILX CWA, across
portions of the lower MS Valley, but the potential exists for
some strong to severe storms locally. Overall, the system seems
progressive enough to limit the flood threat, but will need to
monitor how any convective elements play out. Antecedent
conditions are on the dry side. For now, the WPC Excessive
Rainfall Outlook for Tues/Tues night has a marginal risk across
southern IL (I-64 and south).

In the wake of this system, strong synoptic northwest winds appear
possible on Wed. Will evaluate this potential in greater detail
tomorrow morning.

Erwin

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1127 AM CST Fri Feb 28 2025

A cold front will move across central Illinois this afternoon.
Strong southwest winds gusting 30 to 40 kt will continue ahead of
the front, then will veer to northwesterly behind the front.
Northwest winds will taper some around sunset this evening but
will likely gust at least occasionally in the 20-30 kt range
through the night. VFR conditions will prevail through the period.

Deubelbeiss

&&

.FIRE WEATHER...
Issued at 312 AM CST Fri Feb 28 2025

A combination of strong wind gusts (35 to 50 mph) and warm/dry
conditions will produce elevated fire danger this afternoon. Winds
will be out of the southwest, shifting to west-northwest by mid-
afternoon. The HRRR/RAP continue to exhibit the lowest Td this
afternoon, in the mid/upper 20s. Trended our temperature/dewpoint
forecast towards the 90th/10th percentile of the NBM,
respectively, resulting in minRH values near 25% which is near the
RH threshold for a Red Flag Warning. The limiting factor from
meeting Red Flag Warning is the fuel moisture (10-hour fuel
moisture around 11-15%, criteria is 8%). Nevertheless, last
weekend after we had recent snowmelt to wet the ground, field
fires still grew out of control across east-central IL despite
much weaker winds and wetter fuels than is forecast today. I
expect to see some fires pop-up across the CWA this afternoon, and
any burning by non-professionals has the potential to quickly
grow out of control. A Red Flag Warning was seriously considered,
but since we`re only marginally meeting the RH criteria and not
meeting the fuel criteria, decided to hold off.

Portions of west-central IL were included in the "elevated" category
of the Day 1 SPC Fire Weather Outlook. These are a relatively rare
occurrence in our local area. There were a handful of times our area
was included in such outlooks last October, but before that the
previous occurrence was April 2023.

Erwin

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 9 AM this morning to 2 PM CST this afternoon
for ILZ028-030-031-038-043>046-053>057-062-063-068.

&&

$$


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 6 PM CST this evening for ILZ027>031-
036>038-040>057-061>063-066.

Wind Advisory until 2 PM CST this afternoon for ILZ028-030-031-
038-043>046-053>057-062-063-068.

&&

$$